Sync with https://github.com/robbiehanson/CocoaAsyncSocket and a little tweak to handle Ignite Openfire behaviour

Openfire server strips namespace 'xml' from 'xml:lang', so check for 'xml:lang' and 'lang' attributes when a body with a specific language is requested.

Removed warning from GCDAsyncSocket as it was already done in https://github.com/robbiehanson/CocoaAsyncSocket.